1. Field
The present disclosure relates generally to monitoring aircraft structures and, in particular, to monitoring aircraft structures for inconsistencies. Still more particularly, the present disclosure relates to a method and apparatus for detecting inconsistencies in aircraft structures using signals sent through the aircraft structures.
2. Background
Composite and metallic aircraft structures may be susceptible to internal changes that may occur from fatigue, impacts, and/or other events or conditions. Composite materials typically have a minimal visual indication of these types of changes. As a result, an aircraft may be inspected to access the integrity of the structure on a periodic basis, or after visual indications of surface inconsistencies, such as a dent or a scratch.
For example, impacts to a structure, such as an aircraft, may occur during cargo loading and unloading. Inspections of the structure of an aircraft may be time-consuming and costly in terms of the time and skill needed to perform the inspection. Further, an airline may incur a loss of revenue from the aircraft being out of service.
Structural health monitoring techniques have been developed and used to monitor materials and structures. These techniques often build the health monitoring systems into the structures. These health monitoring systems may be used to determine whether changes have occurred to these materials and structures over time.
Sudden changes in environments, such as electromagnetic effects, mechanical stresses, and other environmental effects may affect various materials and structures over time. By having health monitoring systems built into or associated with the structures to monitor the structures during use, appropriate measures and responses may be taken to prevent inconsistencies and may prolong the life span of these structures.
The monitoring of structures may include various non-destructive elevation methods, such as ultrasonic testing or x-ray testing. Ultrasonic testing uses contact-based transducers to mechanically scan a structure. These transducers may be surface-mounted on the structure or may be embedded in the structure to generate and propagate signals into the structure being monitored.
A structural health monitoring system uses transducers to transmit waveforms at various frequency ranges and acquire data from the responses. Although structural health monitoring systems may provide an automated onboard system for detecting and characterizing inconsistencies or changes that may require maintenance, these types of systems may require updates and adjustments when maintenance, modifications, and reconfigurations of an aircraft occur.
For example, if a skin panel is changed, if a landing gear is modified, or other changes occur, additional transducers may need to be moved or configured for use with the replaced or new components. These and other types of updates to the structural health monitoring system are time consuming and expensive. The time needed to update the health monitoring system may make the aircraft unavailable for use longer than desired.
Therefore, it would be advantageous to have a method and apparatus that takes into account some of the issues discussed above, as well as possibly other issues.